Insulated cargo container doors

ABSTRACT

The prevention discloses an insulated door for a cargo container, and in particular, a boxcar. In one implementation, the door is a double plug door, wherein each door has an insulating layer and a skin on the insulating door. Each door also has a projection designed to overlap with a projection on the other door. A sealing member is also included on one of the doors. When the double plug door of the invention is closed, the only contact between the doors in the area of the projections is between the skin of one door and the skin or sealing member of the second door. This improves the thermal efficiency of the doors.

I. CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Provisional Application No. 60/616,621, filed Oct. 8, 2004, by Joseph A. Seiter and titled Door Seal for an Insulated Railroad Car, the disclosure of which is expressly incorporated herein by reference.

II. BACKGROUND

A. Technical Field

The present invention relates to a door and a door seal for an insulated cargo container. In one embodiment, the door and door seal are for an insulated railroad boxcar.

B. Related Art

Currently, many shippers utilize insulated or refrigerated large cargo containers (such as boxcars) to transport items that require the maintenance of specified temperatures during transit. Because these containers are required to maintain certain temperatures, the thermal efficiency of these containers is an important feature. Thermal efficiency is characterized by the thermal conductivity of a particular component or its inverse, its resistance to heat transfer commonly referred to as an R value.

One area of heat loss in these containers is in the area of the door. Cargo container doors come in various types including sliding and plug doors. Sliding doors are opened and closed by sliding the door along tracks. Plug doors are similar to sliding doors, however, they are designed to close with a final inward movement that positions (or “plugs”) the interior of the door flush with the interior of the car. This flush feature increases the uninterrupted wall space of the car, and facilitates the use of insulation in the door. Plug doors typically have a gasket similar to a refrigerator door so that, when closed, the door seal is water and light resistant.

In the past, cargo container doors were typically constructed of a combination of wood and metal members. Because members of this type typically possessed a low R-value, insulation, such as foam insulation, was often installed in these cargo container doors to increase their thermal efficiency. Even with the use of insulation, however, the thermal efficiency of cargo container doors of this type has not been as high as desired by users of these cargo containers.

In addition, in plug doors, the door seal itself affects the thermal efficiency of the door. In the past, the seal has often acted as a thermal short circuit. A thermal short circuit is an area where heat is able to bypass insulation and therefore more easily transfer through the door. This results in a loss of thermal efficiency.

Therefore, there is a need for a cargo container door constructed to improve thermal efficiency and that also removes potential thermal short circuits. The present invention provides a cargo container door that meets these needs.

II. SUMMARY OF THE INVENTION

Apparatus consistent with one embodiment of the present invention provide a cargo container comprising an enclosure for transporting cargo, the enclosure comprising an opening to provide access to the enclosure, a first plug door, and a second plug door. The first plug door includes a first insulating layer; a first skin on a face of the first insulating layer; and a first projection. The second plug door includes a second insulating layer; a second skin on a face of the second insulating layer; a second projection designed to overlap with the first projection; and a sealing member disposed on the second projection. When the first plug door and the second plug door are in a closed configuration, the only contact between the first plug door and the second plug door in the area of the first and second projections is between the first skin and the second skin or the sealing member.

Apparatus consistent with another embodiment of the present invention provide a cargo container comprising an enclosure for transporting cargo, the enclosure comprising an opening to provide access to the enclosure, a first plug door, and a second plug door. The first plug door includes a first insulating layer; a first outer skin on an outer surface of the first insulating layer; and a first inner skin on an inner surface of the first insulating layer, wherein the inner skin includes a projection. The second plug door includes a second insulating layer; a second outer skin on an outer surface of the second insulating layer; and a second inner skin on an inner surface of the second insulating layer; wherein the second insulating layer, second outer skin, and second inner skin include a second projection designed to overlap with the first projection; and a sealing member disposed on the second projection. When the first plug door and the second plug door are in a closed configuration, the only contact between the first plug door and the second plug door in the area of the first and second projections is between the first inner skin and the second inner skin of the second plug door or the sealing member.

Apparatus consistent with another embodiment of the present invention provide a cargo container comprising an enclosure for transporting cargo, the enclosure comprising an opening to provide access to the enclosure, the opening having a door jamb on its perimiter, and a plug door. The doorjamb includes a first insulating layer; a first skin on a face of the first insulating layer; and a first projection. The plug door includes a second insulating layer; a second skin on a face of the second insulating layer; a second projection designed to overlap with the first projection; and a sealing member disposed on the second projection. When the plug door is in a closed configuration, the only contact between the plug door and the door jamb in the area of the first and second projections is between the first skin and the second skin or the sealing member.

Apparatus consistent with another embodiment of the present invention provide a cargo container comprising an enclosure for transporting cargo, the enclosure comprising an opening to provide access to the enclosure, the opening having a door jamb on its perimiter, and a plug door. The doorjamb includes a first insulating layer; a first outer skin on an outer surface of the first insulating layer; and a first inner skin on an inner surface of the first insulating layer, wherein the inner skin includes a projection. The plug door includes a second insulating layer; a second outer skin on an outer surface of the second insulating layer; and a second inner skin on an inner surface of the second insulating layer; wherein the second insulating layer, second outer skin, and second inner skin include a second projection designed to overlap with the first projection; and a sealing member disposed on the second projection. When the plug door is in the closed configuration, the only contact between the plug door and the door jamb in the area of the first and second projections is between the first inner skin and the second inner skin of the second plug door or the sealing member.

Apparatus consistent with another embodiment of the present invention provide a double plug door for a cargo container. The double plug door includes a first plug door and a second plug door. The first plug door includes a first insulating layer; a first skin on a face of the first insulating layer; and a first projection; and a second plug door comprising: a second insulating layer; a second skin on a face of the second insulating layer; a second projection designed to overlap with the first projection; and a sealing member disposed on the second projection. When the first and second projections overlap, the only contact between the first plug door and the second plug door in the area of the first and second projections is between the first skin and the second skin or the sealing member.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as claimed.

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate several embodiments of the invention and together with the description, serve to explain the principles of the invention.

III. BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of double plug door consistent with one embodiment of the invention;

FIG. 2 is a top perspective cross-sectional view of a double plug door at the abutting portion of the doors consistent with one embodiment of the invention; and

FIG. 3 is a top cross-sectional view of a double plug door at the abutting portion of the doors consistent with one embodiment of the invention.

IV. DESCRIPTION OF THE EMBODIMENTS

A. Introduction

As described below, apparatus consistent with the present invention will now be described with respect to one embodiment of an insulated door for a cargo container: an insulated double plug door for a boxcar. The invention as claimed, however, is broader than insulated double plug doors for boxcars and extends to other plug doors for boxcars, such as single plug doors for boxcars. In addition, the invention as claimed is broader than insulated doors for boxcars and extends to insulated doors for other large insulated cargo containers, such as, shipping containers used on seagoing container vessels, truck trailers, straight trucks, refrigerated buildings, or the like.

B. Apparatus

FIG. 1 is a perspective view of double plug door consistent with one embodiment of the invention. As shown in FIG. 1, a double plug door comprises two doors 24 and 25. Doors 24 and 25 are installed in an opening of a boxcar. In operation, doors 24 and 25 would be slidably mounted on tracks. In order to close off or provide access to the opening, doors 24 and 25 would slide towards one another or away from one another, respectively. As is well known in the design of plug doors, doors 24 and 25 are designed to close with a final inward movement that plugs the interior of doors 24 and 25 flush with the interior of the car and one another. Doors 24 and 25 will typically include handles, such as handles 34 and 36 (not shown in FIG. 1, but shown in FIGS. 2-3) to operate the doors.

Doors 24 and 25 may be constructed entirely of metal, or a combination of metal and composites. Composites are materials made up of a combination of different materials, typically some combination of metals, plastics, and/or ceramics. In one implementation, doors 24 and 25 are constructed of an outer skin 33 and an inner skin 26 (not shown in FIG. 1, but shown in FIGS. 2-3) located on opposing faces of an insulating layer 28 (not shown in FIG. 1, but shown in FIGS. 2-3). In other implementations, outer skin 33 and inner skin 26 will extend over the side surface of insulating layer 28 as well. These implementations are merely exemplary, and other implementations may also be used.

Outer skin 33 and inner skin 26 are constructed of sheet metal, such as galvanized steel, aluminum, stainless steel, coated sheet metal, or fiber-reinforced plastics, or some combination of these materials. In addition, outer skin 33 and inner skin 26 may be constructed to be dent resistant, corrosion resistant, or puncture resistant using the materials described above, as is well known in the art. Also, outer skin 33 and inner skin 26 need not be constructed of the same materials and may have differing mechanical properties. For example, in one implementation, inner skin 26 will be constructed of fiber reinforced plastics, while outer skin 33 will be constructed of galvanized steel. These implementations are merely exemplary, and other implementations may also be used.

Insulating layer 28 may be constructed from any insulating material that will increase the thermal efficiency of doors 24 and 25. In one implementation, insulating layer 28 comprises a closed-cell polymer foam, such as urethane. In another implementation, insulating layer 28 comprises a vacuum insulated panel. Vacuum insulated panels are constructed of an intermediate film or laminate providing a barrier to passage of air into an interior porous insulating material that has been evacuated to increase its insulating value. In one implementation, the interior porous insulating material comprises a micro-cellular open-cell foam core material. In one implementation, the diameter of the cells is on the order of 10⁻⁶ in. A one inch thick sheet of such a material may have a R-value (evacuated) of approximately 28. A micro-cellular, open-cell polystyrene foam, such as Instill™ available from Dow Chemicals may be used in such an implementation. In yet another implementation, the porous insulating material is a fine fiberglass web core material. In one implementation, each fine fiberglass strand will have a diameter of approximately 0.001 in. A one inch thick sheet of such a material may have a R-value (evacuated) of approximately 40. A fine fiberglass web core material such as Threshold™ available from Thermal Visions may be used in such an implementation. In another implementation, insulating layer 28 comprises a combination of foam and vacuum insulated panels. These implementations are merely exemplary, and other implementations may be used.

As described above, doors 24 and 25 are closed by first sliding the doors towards one another. Doors 24 and 25 are then fully closed by a final inward movement. In the case of double plug doors, such as doors 24 and 25, the doors typically include a joint at the point where the doors intersect with one another when closed. Typically, the joint is designed to create a seal when the doors are closed. In the present invention, the joint of doors 24 and 25 is designed to improve the thermal efficiency of doors 24 and 25.

FIGS. 2 and 3 are two cross-sectional views of a double plug door at the abutting portions of the doors consistent with one embodiment of the invention. These cross-sectional views have been taken along line 2 of FIG. 1. As shown in FIGS. 2 and 3, doors 24 and 25 include a joint 30. The doors are not physically attached at the joint 30, they merely abut. The configuration of the joint 30 is commonly known as a “lap joint,” wherein two members overlap. As shown in FIGS. 2 and 3, doors 24 and 25 each include a projection 37 and 38 that overlap with the corresponding projection on the opposing door. Joint 30 also includes a sealing member 32 disposed on one of these projections, in this case, projection 38. When the doors are closed, projection 38 is pressed towards projection 37, which will in turn press sealing member 32 against projection 37. Sealing member 32 will thus be compressed between projections 38 and 37 and will seal the door when closed to improve the thermal performance of the door. FIGS. 2-3 do not show joint 30 in this fully closed configuration.

In one implementation, shown in FIGS. 2 and 3, projection 37 of door 25 is constructed as a flange extending from outer skin 26. In this implementation, projection 37 is constructed of the same material as outer skin 26. In this implementation, projection 38 of door 25 includes outer skin 26, inner skin 33, and insulation layer 28. Projection 38 includes a step 40 to accommodate the sealing member 32 and projection 37. Projections 37 and 38 should be designed to function under the load stresses imposed by the compression of the resilient sealing member 32. These implementations are merely exemplary, and other implementation may also be used.

As shown in FIG. 3, sealing member 32 includes a base 18, which is disposed in the step 40 on the interior surface of projection 38. Though not depicted, sealing member 32 may extend around the entire perimiter of door 24, along the entire joint-side of door 24, or along only a portion of the joint-side of door 24. Sealing member 32 may be formed of any resilient material that act as an effective thermal insulator. In one implementation, sealing member 32 is constructed of a compressible material of low thermal conductivity, such as rubber. These implementations are merely exemplary, and other implementation may also be used.

As shown in FIGS. 2 and 3, in one implementation, sealing member 32 is tubular having a circular cross-section and includes several small projections 41 on its exterior surface 42. The projections 41 on sealing member 32 reduce the area of contact between sealing member 32 and projection 37 and further provides air gaps 43 between sealing member 32 and projection 37. This, in turn, reduces the amount of heat transfer through joint 30. Sealing member 32 may have a shape other than that depicted. For example, sealing member 32 could have an elliptical cross-section or a square cross-section. In addition, sealing member 32 may have any number of projections or no projections at all. These implementations are merely exemplary, and other implementation may also be used.

In the implementation depicted in FIGS. 2 and 3, when doors 24 and 25 are closed, the only contact between the doors in the abutting portion of the doors, occurs between inner skin 26 of door 25 and inner skin 26 of door 24 or between inner skin 26 of door 25 and sealing member 32 of door 24. In this implementation, limiting the points of contact in this manner allows inner skin 26 of doors 24 and 25 and sealing member 32 to function as a thermal break. A thermal break is a an area of low heat conductivity that reduces the heat transfer between two elements. In this case, inner skin 26 of doors 24 and 25 and sealing member 32 reduce heat transfer between the doors and thereby improves the thermal performance of the door. These implementations are merely exemplary, and other implementations may be used.

It should be understood that FIGS. 2 and 3 illustrate only one embodiment of a door joint consistent with the invention. The projections of the door joint may be constructed in any configuration and in any shape provided that contact between the doors is limited to the inner skins and the sealing member.

It should also be understood that while FIGS. 1-3 depict a double plug door, the invention may also be used consistent with a single plug door. In a single plug door, the door jamb and door will form the joint. This joint may be constructed in the same manner as joint 30 described above to achieve similar benefits.

Other embodiments of the invention will be apparent to those skilled in the art from consideration of the specification and practice of the invention disclosed herein. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the invention being indicated by the following claims. 

1. A cargo container comprising: an enclosure for transporting cargo, the enclosure comprising an opening to provide access to the enclosure; a first plug door comprising: a first insulating layer; a first skin on a face of the first insulating layer; and a first projection; and a second plug door comprising: a second insulating layer; a second skin on a face of the second insulating layer; a second projection designed to overlap with the first projection; and a sealing member disposed on the second projection; wherein when the first plug door and the second plug door are in a closed configuration, the only contact between the first plug door and the second plug door in the area of the first and second projections is between the first skin and the second skin or the sealing member.
 2. The cargo container of claim 1, wherein the first and second skins comprise fiber-reinforced plastics.
 3. The cargo container of claim 1, wherein the first and second insulating layers comprise urethane foam.
 4. The cargo container of claim 1, wherein the the first and second insulating layers comprise a vacuum insulated panel.
 5. A cargo container comprising: an enclosure for transporting cargo, the enclosure comprising an opening to provide access to the enclosure; a first plug door comprising: a first insulating layer; a first outer skin on an outer surface of the first insulating layer; and a first inner skin on an inner surface of the first insulating layer, wherein the inner skin includes a projection; and a second plug door comprising: a second insulating layer; a second outer skin on an outer surface of the second insulating layer; and a second inner skin on an inner surface of the second insulating layer; wherein the second insulating layer, second outer skin, and second inner skin include a second projection designed to overlap with the first projection; and a sealing member disposed on the second projection; wherein when the first plug door and the second plug door are in a closed configuration, the only contact between the first plug door and the second plug door in the area of the first and second projections is between the first inner skin and the second inner skin of the second plug door or the sealing member.
 6. The cargo container of claim 5, wherein the first and second inner skins comprise fiber-reinforced plastics.
 7. The cargo container of claim 5, wherein the first and second insulating layers comprise urethane foam.
 8. The cargo container of claim 5, wherein the the first and second insulating layers comprise a vacuum insulated panel.
 9. A cargo container comprising: an enclosure for transporting cargo, the enclosure comprising an opening to provide access to the enclosure, the opening having a doorjamb on its perimiter, wherein the doorjamb includes: a first insulating layer; a first skin on a face of the first insulating layer; and a first projection; and a plug door comprising: a second insulating layer; a second skin on a face of the second insulating layer; a second projection designed to overlap with the first projection; and a sealing member disposed on the second projection; wherein when the plug door is in a closed configuration, the only contact between the plug door and the door jamb in the area of the first and second projections is between the first skin and the second skin or the sealing member.
 10. The cargo container of claim 9, wherein the first and second skins comprise fiber-reinforced plastics.
 11. The cargo container of claim 9, wherein the first and second insulating layers comprise urethane foam.
 12. The cargo container of claim 9, wherein the the first and second insulating layers comprise a vacuum insulated panel.
 13. A cargo container comprising: an enclosure for transporting cargo, the enclosure comprising an opening to provide access to the enclosure, the opening having a doorjamb on its perimiter, wherein the doorjamb includes: a first insulating layer; a first outer skin on an outer surface of the first insulating layer; and a first inner skin on an inner surface of the first insulating layer, wherein the inner skin includes a projection; and a plug door comprising: a second insulating layer; a second outer skin on an outer surface of the second insulating layer; and a second inner skin on an inner surface of the second insulating layer; wherein the second insulating layer, second outer skin, and second inner skin include a second projection designed to overlap with the first projection; and a sealing member disposed on the second projection; wherein when the plug door is in the closed configuration, the only contact between the plug door and the door jamb in the area of the first and second projections is between the first inner skin and the second inner skin of the second plug door or the sealing member.
 14. The cargo container of claim 13, wherein the first and second inner skins comprise fiber-reinforced plastics.
 15. The cargo container of claim 13, wherein the first and second insulating layers comprise urethane foam.
 16. The cargo container of claim 13, wherein the the first and second insulating layers comprise a vacuum insulated panel.
 17. A double plug door for a cargo container comprising: a first plug door comprising: a first insulating layer; a first skin on a face of the first insulating layer; and a first projection; and a second plug door comprising: a second insulating layer; a second skin on a face of the second insulating layer; a second projection designed to overlap with the first projection; and a sealing member disposed on the second projection; wherein when the first and second projections overlap, the only contact between the first plug door and the second plug door in the area of the first and second projections is between the first skin and the second skin or the sealing member.
 18. The cargo container of claim 17, wherein the first and second skins comprise fiber-reinforced plastics.
 19. The cargo container of claim 17, wherein the first and second insulating layers comprise urethane foam.
 20. The cargo container of claim 17, wherein the the first and second insulating layers comprise a vacuum insulated panel. 